package org.yaosheng.algorithm.Data_Structures;

/**
 * Created by yaosheng on 2022/6/12.
 * 循环队列
 */
public class LoopQueue<E> implements Queue<E>{

    private E[] data;
    private int front,tail;
    private int size;

    public LoopQueue(int capacity){
        data = (E[])new Object[capacity + 1];
        front = 0;
        tail = 0;
        size = 0;
    }

    public LoopQueue(){
        this(10);
    }

    public int getCapacity(){
        return data.length - 1;
    }

    @Override
    public int getSize() {
        return size;
    }

    @Override
    public boolean isEmpty() {
        return front == tail;
    }

    @Override
    public void enqueue(E e) {
        if((tail + 1) % data.length == front)
            resize(getCapacity () * 2);

        data[tail] = e;
        tail = (tail + 1) % data.length;
        size ++;
    }

    private void resize(int newCapacity){

        E[] newData = (E[])new Object[newCapacity + 1];
        for(int i = 0;i < size;i ++){
            newData[i] = data[(i + front) % data.length];
        }
        data = newData;
        front = 0;
        tail = size;
    }

    @Override
    public E dequeue() {

        if(isEmpty ())
            throw new IllegalArgumentException ("Cannot dequeue from an empty queue.");

        E ret = data[front];
        data[front] = null;
        front = (front + 1) % data.length;
        size --;
        if(size == getCapacity () / 4 && getCapacity () / 2 != 0)
            resize (getCapacity () / 2);
        return ret;
    }

    @Override
    public E getFront() {
        if(isEmpty ())
            throw new IllegalArgumentException ("Queue is empty.");
        return data[front];
    }

    @Override
    public String toString(){

        StringBuilder res = new StringBuilder ();
        res.append (String.format ("Queue: size = %d, capacity = %d\n",size, getCapacity ()));
        res.append ("front [");
        for(int i = 0;i != tail;i = (i + 1) % data.length){
            res.append (data[i]);
            if((i + 1) % data.length != tail)
                res.append (", ");
        }
        res.append ("] tail");
        return res.toString ();
    }

    public static void main(String[] args) {

        LoopQueue<Integer> queue = new LoopQueue<> ();
        for(int i = 0;i < 10;i ++){
            queue.enqueue (i);
            System.out.println (queue);

            if(i % 3 == 2){
                queue.dequeue ();
                System.out.println (queue);
            }
        }
    }
}
